The present invention relates generally to integrated circuit packaging, and, more particularly, to an integrated circuit structure that facilitates attaching the die to a substrate.
In a conventional packaged integrated circuit (IC) device, an IC die is typically mounted on and attached to another component of the IC device such as a lead frame flag (also referred to as a die paddle), a substrate, or another IC die. To mount and attach the IC die, a dispenser dispenses a controlled amount of a die attach adhesive onto the other component. Then, pick-and-place machinery presses the IC die into the die attach adhesive.
FIGS. 1A-1E show cross-sectional side views of a few different ways in which a conventional IC die 100 may be mounted on a lead frame flag 108 using a die attach adhesive 106. In general, the IC die 100 has an active side 102 having bond pads (not shown) disposed thereon and an inactive side 104 without bond pads. The pick-and-place machinery (not shown) places the IC die 100 on the die attach adhesive 106 such that the inactive side 104 of the IC die 100 is oriented toward the lead frame flag 108 and the active side 102 of the IC die 100 is oriented away from the lead frame flag 108 (i.e., facing up).
FIG. 1A shows the IC die 100 properly mounted properly on the lead frame flag 108. The amount of the adhesive 106 dispensed is sufficient to ensure that the adhesive 106 covers the entire inactive side 104 of the IC die 100 and only a small portion of the sides of the IC die 100. Further, the adhesive 106 does not have any air pockets or voids formed therein. The IC die 100 is positioned such that the inactive side 104 is substantially parallel to the upper surface of the lead frame flag 108. This ensures that the bond-line thickness (i.e., the die attach material thickness between the die's inactive side 104 and the upper surface of the flag 108) is substantially uniform across the entire area beneath the inactive side 104.
FIGS. 1B-1E illustrate a few of the issues that may arise when mounting the IC die 100 on the other component. In FIG. 1B, an insufficient amount of the adhesive 106 is dispensed onto the flag 108. As a result, when the IC die 100 is placed on the adhesive 106, the adhesive 106 does not cover the entire inactive side 104 of the IC die 100.
In FIG. 1C, the IC die 100 is pressed too far into the adhesive 106. As a result, the adhesive 106 extends up the sides of the IC die 100, and possibly contaminating the active side 102 of the IC die 100. Note that, whether or not the adhesive 106 extends up the sides of the IC die 100 is a function of the amount of adhesive 106 applied. Further, the bond-line thickness beneath the IC die 100 is small, which could adversely affect the reliability of the bond or possibly lead to cracking of the IC die 100 due to coefficient of thermal expansion (CTE) mismatch between the die 100, the adhesive 106, and the lead frame flag 108 during temperature cycling.
In FIG. 1D, the IC die 100 is mounted at an angle such that the inactive side 104 of the IC die 100 is not substantially parallel to the upper surface of the flag 108. As a result, the bond-line thickness is not uniform, which could adversely affect the reliability of the bond or possibly lead to cracking of the IC die 100 as discussed above.
In FIG. 1E, a void 110 is formed in the adhesive 106 when the IC die 100 is pressed into the adhesives 106. This void 110 could adversely affect the reliability of the bond between the IC die 100 and the flag 108, or possibly lead to electrical overstress. Accordingly, it would be advantageous to be able to mount and attach a die to another component in a manner that does not encounter the above-identified issues.